1. Field of the Invention
The present invention relates to a plasma display panel. More particularly, the present invention relates to a plasma display panel that may improve discharge uniformity by varying a permittivity of a dielectric layer according to a size of a discharge gap.
2. Description of the Related Art
A plasma display panel may generally use vacuum ultraviolet (VUV) rays emitted from plasma generated by gas discharge so as to excite a phosphor material. The excited phosphor material may generate red (R), green (G), and blue (B) visible light beams, so that an image may be displayed.
In an AC type plasma display panel, address electrodes may be formed on a rear substrate. The address electrodes may be covered with a dielectric layer. Barrier ribs may respectively be arranged in a stripe pattern between the address electrodes on the dielectric layer. R, G, and B phosphor layers may be in the barrier ribs. A front substrate may face the rear substrate. Display electrodes constructed with pairs of sustain electrodes and scan electrodes may be on the front substrate in a direction crossing the address electrodes. The display electrodes may be covered with a dielectric layer and an MgO protective layer. Discharge cells may be at a portion where the address electrodes on the rear substrate cross the display electrodes on the front substrate. Millions or more of unit discharge cells may be arranged in the plasma display panel in a matrix pattern.
Memory characteristics may be used to drive the discharge cells of the plasma display panel. Specifically, in order for a discharge to occur between the sustain electrodes and the scan electrodes constituting the display electrodes, an electric potential difference over a predetermined voltage may be required. A threshold voltage thereof may be a firing voltage Vf. When a scan voltage and an address voltage are respectively supplied to the scan electrodes and the address electrodes, a discharge may initially occur to produce plasma in the discharge cells. Electrons and ions of the plasma may be transferred towards an electrode having an opposite polarity.
Each electrode of the plasma display panel may be coated with a dielectric layer. Most of transferred space charges may be accumulated on the dielectric layer having an opposite polarity. Therefore, a net space voltage between the scan electrodes and the address electrodes may become lower than an initially provided address voltage Va. As a result, a discharge may diminish, and an address discharge may disappear. In this case, the amount of electrons accumulated in the sustain electrodes may be relatively small, while the amount of ions accumulated in the scan electrodes may be relatively large. Charges accumulated on the dielectric layer covering the sustain electrodes and the scan electrodes may be wall charges Qw. A space voltage produced between the sustain electrodes and the scan electrodes by the wall charges Qw may be a wall voltage Vw.
When a discharge sustain voltage Vs is supplied to the sustain electrodes and the scan electrodes, if a sum voltage Vs+Vw of the discharge sustain voltage Vs and the wall voltage Vw is greater than the firing voltage Vf, a sustain discharge may occur in the discharge cells. As a result, a VUV ray may be generated to excite a corresponding phosphor layer. Accordingly, a visible light beam may be emitted through the transparent front substrate.
When the address discharge does not occur between the scan electrodes and the address electrodes (that is, when the address voltage Va is not provided), the wall charges Qw may not accumulate between the sustain electrodes and the scan electrodes. As a result, the wall voltage Vw may not exist between the sustain electrodes and the scan electrodes. In this case, only the discharge sustain voltage Vs supplied to the sustain electrodes and the scan electrodes may be produced in the discharge cells. Since the discharge sustain voltage Vs may be lower than the firing voltage Vf, a discharge may not occur in a gas space between the sustain electrodes and the scan electrodes.
In the plasma display panel driven in the aforementioned manner, a discharge gap may be formed between a transparent electrode of the sustain electrode and a transparent electrode of the scan electrode.
Referring to FIG. 9, discharge cells LC each having a relatively long gap may have a high firing voltage, and discharge cells SC each having a short gap may have a low firing voltage. Discharge cells MC each having a medium firing voltage may have a firing voltage between the high firing voltage and the low firing voltage.
The transparent electrodes may be formed by using various methods, e.g., an etching method. However, it may be difficult to form the transparent electrodes to have uniform sizes due to manufacturing errors. In this case, the transparent electrodes of the plasma display panel may have irregular sizes, and thus a discharge gap also may become irregular. As a result, there may be problems arising from a firing voltage becomes irregular.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.